# SEMINAR

SU(5)$otimes$Z$_{13}$ Grand Unification Model
* Edison T. Franco*
(**CFTP-IST & IFT-UNESP, S.Paulo, Brazil**)

**Sala P7, IST, EdifĂcio MatemĂˇtica**

**Thursday, February 5th, 2009 at 04:00 PM**

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**Abstract**
`
We propose an $SU(5)$ grand unified model with an invisible axion and the
unification of the three coupling constants which is in agreement with the
values, at $M_Z$, of $\alpha$, $\alpha_s$, and $\sin^2\theta_W$. A
discrete, anomalous, $Z_{13}$ symmetry implies that the PQ symmetry is an
automatic symmetry of the classical Lagrangian protecting, at the same
time, the invisible axion against possible semi-classical gravity effects.
Although the unification scale is of the order of the PQ scale the proton
is stabilized by the fact that in this model the standard model fields
form the $SU(5)$ multiplets completed by new exotic fields and, also,
because it is protected by the $Z_{13}$ symmetry.`

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